Structural analysis of stereoselective galactose pyruvylation toward the synthesis of bacterial capsular polysaccharides

• Tsun-Yi Chiang,
• Mei-Huei Lin,
• Chun-Wei Chang,
• Jinq-Chyi Lee and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2025, 21, 1671–1677, doi:10.3762/bjoc.21.131

• 10 was formed, giving 71% yield (α/β = 1:6). According to the RRV/Aka platform [44], compound 9 is a robust nucleophile, with an Aka value of 12 [45]. This high nucleophilicity favors a SN2-like mechanism, promoting β-selectivity [46]. Using the difference in acceptor reactivity and activation method

Influence of the cation in hypophosphite-mediated catalyst-free reductive amination

• Natalia Lebedeva,
• Fedor Kliuev,
• Olesya Zvereva,
• Klim Biriukov,
• Evgeniya Podyacheva,
• Maria Godovikova,
• Oleg I. Afanasyev and
• Denis Chusov

Beilstein J. Org. Chem. 2025, 21, 1661–1670, doi:10.3762/bjoc.21.130

• . The remedy for Parkinson’s disease, piribedil, was obtained in high yield. The plausible mechanism of the elaborated process was proposed and supported by DFT calculations. Keywords: amines; DFT; hypophosphites; reductive amination; role of cations; Introduction Sodium hypophosphite, NaH2PO2, is one

• , the synthesis of the remedy for Parkinson’s disease, piribedil (9), in high yield (80%) demonstrated the practical utility of the elaborated synthetic method (Figure 1). To get insight into the mechanism of the developed approach the reaction mixtures were thoroughly analyzed and several control

• identify the rate-determining step clearly, they showed the high rate of exchange through tautomeric equilibria compared to the reduction step. Based on control experiments and previously obtained data [20], we suggested a plausible mechanism of the developed reaction. Its possibility was supported using

Catalytic asymmetric reactions of isocyanides for constructing non-central chirality

• Jia-Yu Liao

Beilstein J. Org. Chem. 2025, 21, 1648–1660, doi:10.3762/bjoc.21.129

• the reaction, the resulting deacylated compound 20 could be recovered in almost quantitative yield without any erosion of the enantiopurity. A possible reaction mechanism for this Pd-catalyzed three-component reaction was proposed (Scheme 3b). As shown, the reaction started with the oxidative addition

• between β-ketoester 30 and di-tert-butyl azodicarboxylate (31), and the corresponding product 32 was obtained in 99% yield with 88% ee. A plausible reaction mechanism was proposed for this CPA-catalyzed enantioselective Groebke–Blackburn–Bienaymé reaction. As illustrated in Scheme 5b, the imine

3-Aryl-2H-azirines as annulation reagents in the Ni(II)-catalyzed synthesis of 1H-benzo[4,5]thieno[3,2-b]pyrroles

• Julia I. Pavlenko,
• Pavel A. Sakharov,
• Anastasiya V. Agafonova,
• Derenik A. Isadzhanyan,
• Alexander F. Khlebnikov and
• Mikhail S. Novikov

Beilstein J. Org. Chem. 2025, 21, 1595–1602, doi:10.3762/bjoc.21.123

• an ortho-substituent into the benzene ring also has no effect on the synthesis efficiency (compound 3f). A slight decrease in yield was observed only for the naphthyl-substituted annulation product 3k. The plausible mechanism of the reaction involves the nucleophilic addition of the Ni-enolate of 1

• the NHC-complex, IPrCuCl, the formation of cycloadduct 11 was detected, which was isolated in 10% yield (Scheme 6). The formation of this compound implies the cleavage of the azirine N−C2 bond, indicating that the IPrCuCl-catalyzed reaction proceeds by a different mechanism, likely involving the

• . Synthesis of fused pyrroles and azoles by [3 + 2] annulation reactions of azirines. Synthesis of benzo[4,5]thieno[3,2-b]pyrroles 3. Plausible mechanism for the formation of compounds 3. Post-modifications of 1H-benzo[4,5]thieno[3,2-b]pyrrole (3b). Synthesis of pyrrolo[3,2-b]indole 10. IPrCuCl-catalyzed

General method for the synthesis of enaminones via photocatalysis

• Paula Pérez-Ramos,
• Raquel G. Soengas and
• Humberto Rodríguez-Solla

Beilstein J. Org. Chem. 2025, 21, 1535–1543, doi:10.3762/bjoc.21.116

• semipreparative scale for the reaction of 3-bromochromone (7a, 5.0 mmol) to afford enaminone 9a in a 68% isolated yield (Scheme 3). In terms of the reaction mechanism, TEMPO completely inhibited the reaction, implying the possibility of a radical intermediate in the reaction (Scheme 4A). Moreover, the TEMPO

• mechanism for this reaction is proposed in Scheme 5. A ternary complex is initially formed upon complexation of 3-bromochromone (7a) with NiBr2-dmbpy. By virtue of being coordinated to a Ni-center, the β-carbon is activated toward nucleophilic attack of the amine, furnishing 2-amino-3-bromochromenone I

• photocatalyst. Examples of compounds with medicinal effects containing an enaminone structural moiety. Synthesis of enaminones. Substrate scope. Scale-up synthesis of enaminone 9a. Mechanistic studies. Proposed mechanism. Optimization of reaction conditions. Supporting Information Supporting Information File 6

Azobenzene protonation as a tool for temperature sensing

• Antti Siiskonen,
• Sami Vesamäki and
• Arri Priimagi

Beilstein J. Org. Chem. 2025, 21, 1528–1534, doi:10.3762/bjoc.21.115

• heavy metal detection [16][19] and humidity sensing [20]. The color changes can be either reversible or irreversible, depending on the mechanism of operation. Spectral tuning also enables switching with low-energy light, eliminating the need for potentially harmful UV irradiation [21]. Utilizing

• spectral changes caused by azobenzene protonation is a well-established concept, with methyl orange-based pH indicators dating back to the late 1800s [22]. Early studies primarily focused on characterizing these spectral changes, determining pKa values, and elucidating the protonation mechanism of

Calcium waste as a catalyst in the transesterification for demanding esters: scalability perspective

• Anton N. Potorochenko and
• Konstantin S. Rodygin

Beilstein J. Org. Chem. 2025, 21, 1520–1527, doi:10.3762/bjoc.21.114

• , and minor components did not affect the reaction or were inert. Since the transesterification with a catalyst derived from carbide slag (CS600) and commercial (or obtained from another source) calcium oxide proceeds by the same mechanism with the formation of a new ester and an alcohol as byproduct

Ambident reactivity of enolizable 5-mercapto-1H-tetrazoles in trapping reactions with in situ-generated thiocarbonyl S-methanides derived from sterically crowded cycloaliphatic thioketones

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Marcin Palusiak,
• Heinz Heimgartner,
• Marta Denel-Bobrowska and
• Agnieszka B. Olejniczak

Beilstein J. Org. Chem. 2025, 21, 1508–1519, doi:10.3762/bjoc.21.113

• chemoselectivity was observed. A detailed study on the mechanism of these reactions showed that the initially formed S–H insertion products (type 5) underwent thermal isomerization leading to thermodynamically more stable N–H insertion ones (type 6) (Scheme 2) and the isomerization process was clearly dependent on

• observed in the 1H NMR spectra registered for crude reaction mixtures (Table 1). The mechanism of the studied reactions deserves a brief comment and should help to clarify whether the formation of 9 and 10 results from the ambident reactivity of 5-mercapto-1H-tetrazoles, suggested in some earlier

• the in situ-generated thiocarbonyl S-methanides 1 (from 1,3,4-thiadiazolines 2) with enolizable 5-mercapto-1H-tetrazoles 4, leading to the N- or S-insertion products 9 and 10, respectively. Stepwise mechanism of the competitive N- and S-insertion reactions between the in situ-generated thiocarbonyl S

Photoredox-catalyzed arylation of isonitriles by diaryliodonium salts towards benzamides

• Nadezhda M. Metalnikova,
• Nikita S. Antonkin,
• Tuan K. Nguyen,
• Natalia S. Soldatova,
• Alexander V. Nyuchev,
• Mikhail A. Kinzhalov and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2025, 21, 1480–1488, doi:10.3762/bjoc.21.110

• diaryliodonium salts under photoredox conditions has been proposed for the first time. The suggested procedure allows preparing a broad range of benzamides using both symmetric and unsymmetric diaryliodonium salts under mild conditions. A plausible mechanism for the reaction and the selectivity of aryl transfer

• reactivity pattern in the current transformation, a reaction mechanism was proposed taking into the account the known data and control experiments (Scheme 4). Upon irradiation with blue light, the Ru(II) catalyst undergoes photoexcitation, followed by an oxidative single-electron transfer (SET) process with

• using 1,2-dibromoethane as an internal standard. cNot detected by GC–MS. Proposed reaction mechanism. Optimization of the reaction conditions.a Supporting Information Supporting Information File 32: Experimental section, characterization data and control experiments. Acknowledgements Authors

Microwave-enhanced additive-free C–H amination of benzoxazoles catalysed by supported copper

• Andrei Paraschiv,
• Valentina Maruzzo,
• Filippo Pettazzi,
• Stefano Magliocco,
• Paolo Inaudi,
• Daria Brambilla,
• Gloria Berlier,
• Giancarlo Cravotto and
• Katia Martina

Beilstein J. Org. Chem. 2025, 21, 1462–1476, doi:10.3762/bjoc.21.108

• open derivative, and the subsequent ring oxidation upon closure (as shown in the mechanism in Scheme S1 (Supporting Information File 1), the reaction mixture may contain the desired 2-substituted benzoxazole 2a together with its open-form precursor 2a-o. The latter can be hydrolysed to give N

• reaction conditions both in terms of temperature and time, as observed using a lower catalyst amount. This assumption was confirmed when the reaction was performed in a MW reactor under 5 bar of N2; in this environment, the copper catalyst cannot regenerate because of the absence of oxygen (see mechanism

Wittig reaction of cyclobisbiphenylenecarbonyl

• Taito Moribe,
• Junichiro Hirano,
• Hideaki Takano,
• Hiroshi Shinokubo and
• Norihito Fukui

Beilstein J. Org. Chem. 2025, 21, 1454–1461, doi:10.3762/bjoc.21.107

• absence of carbonyl groups in bis-olefin 5 has been corroborated by Fourier transform infrared (FTIR) spectroscopy (Figure S16 in Supporting Information File 1). Compound 4 could be generated through the reaction of compound 3 with phosphorus ylide. However, a reliable reaction mechanism remains unclear

• . A tentative mechanism that may be plausible is shown in Supporting Information File 1, Figure S21, which consists of (1) the nucleophilic attack of methylenetriphenylphosphorane to the exo-methylene group of 3, (2) the intramolecular carbon–carbon-bond formation at the carbonyl group, and (3) the

Advances in nitrogen-containing helicenes: synthesis, chiroptical properties, and optoelectronic applications

• Meng Qiu,
• Jing Du,
• Nai-Te Yao,
• Xin-Yue Wang and
• Han-Yuan Gong

Beilstein J. Org. Chem. 2025, 21, 1422–1453, doi:10.3762/bjoc.21.106

• -containing hetero[5]- and [6]helicene-like structures 68a–g in high yields [82]. These compounds display diverse photophysical behaviors: compound 68d emits yellow fluorescence in both solution and solid state, exhibiting solvatofluorochromism due to a twisted intramolecular charge transfer (TICT) mechanism

Tautomerism and switching in 7-hydroxy-8-(azophenyl)quinoline and similar compounds

• Lidia Zaharieva,
• Vera Deneva,
• Fadhil S. Kamounah,
• Nikolay Vassilev,
• Ivan Angelov,
• Michael Pittelkow and
• Liudmil Antonov

Beilstein J. Org. Chem. 2025, 21, 1404–1421, doi:10.3762/bjoc.21.105

• . According to them neither 1 nor 2 is suitable for switching from E to K for couple of reasons. The most important one is the higher relative energy of K in respect of KK. This means that if KK is populated, according to the above described mechanism, the tautomeric proton cannot be released to K, i.e. the

• presented as relative energies in kcal/mol. The values of the angles α and β (see also Scheme 2) are given in brackets (β is underlined). The asterisk indicates trans to cis isomerization via inversion mechanism [67]. In the excited state the relative energy is followed by the oscillator strength of the

High-pressure activation for the solvent- and catalyst-free syntheses of heterocycles, pharmaceuticals and esters

• Kelsey Plasse,
• Valerie Wright,
• Guoshu Xie,
• R. Bernadett Vlocskó,
• Alexander Lazarev and
• Béla Török

Beilstein J. Org. Chem. 2025, 21, 1374–1387, doi:10.3762/bjoc.21.102

• synthesis is still in its infancy. Despite the recent advances [10][11], the HHP applications in this field are still being developed. The first HHP-assisted organic syntheses were reported in the 1970s [12][13]. Although the mechanism of how pressure enables reactions is not fully elucidated, there is a

• full analysis can be obtained by also evaluating the activation volume (ΔV‡) data. Considering that all of the above studied reactions are multistep processes with several elementary steps, the determination of ΔV‡ requires a detailed theoretical reaction mechanism study that is beyond the scope of the

Oxetanes: formation, reactivity and total syntheses of natural products

• Peter Gabko,
• Martin Kalník and
• Maroš Bella

Beilstein J. Org. Chem. 2025, 21, 1324–1373, doi:10.3762/bjoc.21.101

• /RPC mechanism starts with a single-electron oxidation of the cobalt catalyst followed by a reaction with the siloxane to generate a cobalt–hydride complex. Subsequent hydride transfer to the alkene produces radical pair 23 which collapses to alkylcobalt intermediate 24. Another single-electron

• -mediated intramolecular cross-couplings, 2-alkylideneoxetanes can also be accessed by formal [2 + 2] cycloadditions, which are discussed in chapter 1.3.2. 1.2 C–C Bond-forming cyclisations This relatively uncommon strategy is usually based on an ionic mechanism in which an SN2 substitution takes place

• polysubstituted oxetanes 64 (Scheme 18) [57]. The mechanism is based on a 1,5-HAT/radical recombination sequence where the H-atom transfer is triggered by an S0 → T1 excitation of the starting allyl ether 63 using an iridium photosensitiser and blue light for irradiation. The method employs mild reaction

Recent advances and future challenges in the bottom-up synthesis of azulene-embedded nanographenes

• Bartłomiej Pigulski

Beilstein J. Org. Chem. 2025, 21, 1272–1305, doi:10.3762/bjoc.21.99

• of a naphthalene-bridged double [6]helicene (Scheme 6) [46]. Depending on the amount of DDQ used for oxidation, the yield of 36 reached up to 22%, while 37 was obtained in up to 27% yield. The proposed mechanism for the formation of 36 and 37 involves an arenium ion-mediated 1,2-phenyl shift followed

• by a naphthalene-to-azulene rearrangement. The alternative radical cation mechanism has a higher energy barrier than the arenium cation-mediated reaction. Notably, only one of the pentagon–heptagon pairs exhibits an azulene-like electronic structure and aromaticity, as confirmed by the analysis of

• mechanism and 1,2-phenyl shift. However, in this case, analysis of NICS values indicated that the azulene moiety does not exhibit aromatic character, and the electronic properties of the final molecules are primarily determined by the surrounding benzenoid rings. Mastalerz and co-workers reported the

Recent advances in oxidative radical difunctionalization of N-arylacrylamides enabled by carbon radical reagents

• Jiangfei Chen,
• Yi-Lin Qu,
• Ming Yuan,
• Xiang-Mei Wu,
• Heng-Pei Jiang,
• Ying Fu and
• Shengrong Guo

Beilstein J. Org. Chem. 2025, 21, 1207–1271, doi:10.3762/bjoc.21.98

• -methylpiperidine, proved compatible with the reaction conditions, yielding the corresponding 3-(2-oxoethyl)indolin-2-ones 5a–g in 40–78% yields. Following a detailed investigation, a plausible mechanism was proposed, as illustrated in Scheme 3. Initially, TBHP undergoes cleavage by Fe2+ to generate a tert-butoxy

• -free synthetic method for 3,3-disubstituted oxindoles via 1,2-alkylarylation of activated alkenes with alcohols [4]. N-Arylacrylamides and simple alcohols were employed as substrates, proceeding through an oxidative radical cyclization mechanism. The standard reaction conditions involved the use of an

• demonstrated that both primary and secondary alcohols were compatible substrates (7a, 7f). The proposed reaction mechanism involves oxidative radical cyclization. Initially, TBHP undergoes homolytic cleavage to generate a tert-butoxy radical, which then forms an α-hydroxy carbon radical. This radical

Synthesis of β-ketophosphonates through aerobic copper(II)-mediated phosphorylation of enol acetates

• Alexander S. Budnikov,
• Igor B. Krylov,
• Fedor K. Monin,
• Valentina M. Merkulova,
• Alexey I. Ilovaisky,
• Liu Yan,
• Bing Yu and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2025, 21, 1192–1200, doi:10.3762/bjoc.21.96

• isolated in 77% yield (1.3 g, 4.61 mmol). In order to propose the reaction mechanism, control experiments were conducted (Scheme 4). The reaction is completely inhibited by the addition of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) or BHT (Scheme 4, reaction 1). A BHT-adduct derived from a P-centered

• radical was detected by HRMS, which supported a radical mechanism. Next, the influence of the atmosphere and the role of copper catalyst was evaluated (Scheme 4, reaction 2). Neither under argon nor under an oxygen atmosphere, the yield of 3a did not exceed 22%. However, employing 200 mol % of copper(II

• results and previous reports on copper(II) mediated oxyphosphorylation reactions [42][44][46][51][53], a plausible reaction mechanism is proposed (Scheme 5). The discovered transformation is unlikely to proceed via only a single route (see control experiments in Scheme 4), and the generation of phosphorus

Enhancing chemical synthesis planning: automated quantum mechanics-based regioselectivity prediction for C–H activation with directing groups

• Julius Seumer,
• Nicolai Ree and
• Jan H. Jensen

Beilstein J. Org. Chem. 2025, 21, 1171–1182, doi:10.3762/bjoc.21.94

• , thereby dictating the site of C–H activation. Common DGs include unsaturated heteroatoms and alkenyl groups, which have proven effective in guiding the regioselectivity of these reactions [4]. Mechanistic studies with palladium(II) acetate (Pd(OAc)2) as catalyst support the following mechanism of C–H

• activation, called concerted metal deprotonation (CMD) [5][6][7]. In a concerted mechanism, the Pd atom of the catalyst forms a sigma bond to an aromatic carbon, which increases the acidity of the adjacent (alpha) proton. This allows for the simultaneous abstraction of this proton by a carboxylate ligand. A

• electrophilic aromatic substitution and a proton abstraction mechanism via CMD, where they calculated the relative energies of the intermediates. Using their workflow, they were able to predict correctly the regioselectivity for 18 tested substrates. The main limitation of this work is the computational cost

A multicomponent reaction-initiated synthesis of imidazopyridine-fused isoquinolinones

• Ashutosh Nath,
• John Mark Awad and
• Wei Zhang

Beilstein J. Org. Chem. 2025, 21, 1161–1169, doi:10.3762/bjoc.21.92

• (IMDA), and dehydrative re-aromatization reactions for the synthesis of imidazopyridine-fused isoquinolinones is developed. Gaussian computation analysis on the effect of the substitution groups for the IMDA reaction is performed to understand the reaction mechanism. Keywords: Groebke–Blackburn

Investigations of amination reactions on an antimalarial 1,2,4-triazolo[4,3-a]pyrazine scaffold

• Henry S. T. Smith,
• Ben Giuliani,
• Kanchana Wijesekera,
• Kah Yean Lum,
• Sandra Duffy,
• Aaron Lock,
• Jonathan M. White,
• Vicky M. Avery and
• Rohan A. Davis

Beilstein J. Org. Chem. 2025, 21, 1126–1134, doi:10.3762/bjoc.21.90

• Plasmodium parasites and recommends artemisinin combination therapy (ACT) for the treatment of both uncomplicated and severe malaria as a frontline treatment [1]. ACT includes the use of an artemisinin agent in concert with a partner drug (most often a quinoline drug), which possesses a different mechanism

• -position (tele-substituted; Figure 1), distant from the halogen leaving group at position 5 [10]. A plausible reaction mechanism was proposed by Korsik et al. [10]. The antimalarial activity of series 4 triazolopyrazine scaffolds is generally reduced by substitution of an amine functionality at the 8

Gold extraction at the molecular level using α- and β-cyclodextrins

• Susana Santos Braga

Beilstein J. Org. Chem. 2025, 21, 1116–1125, doi:10.3762/bjoc.21.89

• . C skyblue, O red, Br brown, Au yellow. (c) Schematic illustration of the mechanism leading to precipitation (named “supramolecular polymerisation” by the authors) after adding various additives to the solution of β-CD and [AuBr4]− anions. Reproduced from [51] (© 2023 H. Wu et al., published by

Salen–scandium(III) complex-catalyzed asymmetric (3 + 2) annulation of aziridines and aldehydes

• Linqiang Wang and
• Jiaxi Xu

Beilstein J. Org. Chem. 2025, 21, 1087–1094, doi:10.3762/bjoc.21.86

• enantioselectivities and high diastereoselectivities. A reasonable reaction mechanism was proposed and rationalized the experimental results. Keywords: aldehyde; annulation; aziridine; oxazolidine; ring expansion; scandium triflate; Introduction Oxazolidine derivatives are an important class of nitrogen and oxygen

• uses readily available components. On the basis of the experimental results and a previous report [16], a possible reaction mechanism is presented in Scheme 3. The catalyst (Cat) is first generated from salen L1 and Sc(OTf)3. Aziridines 1 coordinate to the Sc ion in the catalyst with their two

• functionalized oxazolidine derivatives in moderate to good yields and good to excellent enantioselectivities and high diastereoselectivities. The stereocontrol was rationalized in the proposed reaction mechanism. Experimental Unless otherwise noted, all materials were purchased from commercial suppliers. Toluene

Recent advances in synthetic approaches for bioactive cinnamic acid derivatives

• Betty A. Kustiana,
• Galuh Widiyarti and
• Teni Ernawati

Beilstein J. Org. Chem. 2025, 21, 1031–1086, doi:10.3762/bjoc.21.85

• –380 via an α-borylation–protodeborylaton mechanism involving intermediates 381 and 382 (Scheme 83A) [141]. On the one hand, Vilotijevic and co-workers (2021) reported a phosphine-mediated partial hydrogenation of conjugated alkynes using water as the hydrogen source to obtain the corresponding cis

• migratory insertion (407) (Scheme 86A) [145]. On the other hand, Werner and Liu (2020) reported a Mn-catalyzed coupling of alcohols and phosphorus ylide 408 to afford the corresponding E-isomers of cinnamate esters 409–411 via an acceptorless dehydrogenative coupling mechanism (Scheme 86B) [146]. In

Pd-Catalyzed asymmetric allylic amination with isatin using a P,olefin-type chiral ligand with C–N bond axial chirality

• Natsume Akimoto,
• Kaho Takaya,
• Yoshio Kasashima,
• Kohei Watanabe,
• Yasushi Yoshida and
• Takashi Mino

Beilstein J. Org. Chem. 2025, 21, 1018–1023, doi:10.3762/bjoc.21.83

• -catalyzed asymmetric allylic amination of allyl esters with isatin using (aR)-(−)-6 possesses an S-configuration. This stereochemical outcome follows the same reaction mechanism as the Pd-catalyzed asymmetric allylic substitution of allyl esters with indoles using (aR)-(−)-6 [31]. To explore further

• allylic amination of acetate 12 with isatin (11a).a Supporting Information Data of thermal racemization of 7, DFT calculations for investigating racemization mechanism of 7, general methods and materials, experimental procedures and characterization data, 1H, 13C and 31P NMR spectra for 9 and 10, 1H, 13C